In power converters with integrated magnetic components and converters with analogous magnetic components, E/ER cores are provided. The term “E/ER core” should be understood as “E core and/or ER core”. Windings of a transformer and a filter output inductor are arranged on winding bobbins, which are further arranged on legs of the E/ER core. Switched mode power converters and specifically DC/DC power converters are widely used in telecommunication and commercial systems, for example, and improvements in this field of technology are of high importance, in particular improvements with respect to power density, reduced costs, lowered losses, and/or improved efficiency as well as thermal resistance.
Active clamp forward converters are one of the most appropriate topologies for low to medium power applications, due to its simplicity and its performance in this power range. While the transformer core is optimally used due to symmetrical excitation in two quadrants of the B-H plane, the output ripple is relatively large and a large output filtering inductor is required, which restricts the power density and efficiency.
For medium to large power applications, two-transistor forward converters are one of the most suitable topologies due to its simplicity and electrical performance. The transformer is excited only in the first quadrant of the B-H plane and the output current ripple is relatively large. Large transformer and output filtering inductors are required, which limits the power density and efficiency.
In order to reduce the size of the components and improve efficiency, integrated magnetic structures have been proposed for active clamp and two-transistor forward converters, wherein all transformer and inductor windings are wound on a single core.
U.S. Pat. No. 5,920,473 (Sturgeon) relates to dc-to-dc power converters with an integrated magnetic power transformer for continuously delivering controllable power to a load. A power transformer has a primary winding, two secondary windings and inductances in series with the primary winding and each of the two secondary windings. The primary and secondary windings are wound on a single magnetic core. The core includes a first leg and an oppositely disposed second leg, a third leg and an oppositely disposed fourth leg. Primary and secondary windings may be wound on one or two legs of the core, wherein the windings are wound spaced apart. An air-gap leg may be disposed between legs. The core may be in the form of a toroid.
Forward converters in the state of the art either require winding bobbins or core arrangements with pair of legs disposed opposed to each other. Winding bobbins lead to undesired losses, whereas disposing legs opposing each other requires complicated assembly steps. These cores are not flexible in term of mounting and of adjusting the magnetizing and filtering inductance through air gap. A single air gap is manufactured on the centre leg of an E/ER core by machine and bobbins are unavoidable to wind the coils. The single air gap, the winding bobbin, and the inflexible assembly affect negatively the costs, the power density, the power efficiency, and the thermal distribution. The winding bobbins and single air gap lead to high costs and cause more leakage as well as inductance losses.